Certain kinds of carboxamide derivatives have been known to have microbicidal activity (see Patent Literature 1 to 12). However, the literature does not describe that these compounds are effective for the disinfection or control of endoparasites in animals such as mammals and birds. It is also known that certain kinds of carboxamide derivatives are effective against nematodes that may damage agricultural products (see Patent Literature 4 or 5), but there is no specific disclosure as to whether these compounds are effective against endoparasites in animals. Furthermore, there is a report that compounds that inhibit succinate-ubiquinone reductase (mitochondrial complex II), which is one of the respiratory enzymes of endoparasites, can serve as an endoparasite control agent (see Non Patent Literature 1).
In addition, Patent Literature 13 discloses certain kinds of carboxamide derivatives which are effective against endoparasites. However, there is no disclosure of the effects of the compounds of the present invention against endoparasites.
Generally, parasitosis is caused by infestation of host animals with parasites such as unicellular protists (protozoa), multicellular helminths and arthropods. It is reported that the incidence of parasitosis in Japan has been remarkably decreased by improvement of environmental hygiene, but on a global scale, particularly in developing countries, parasitosis still widely prevails and causes tremendous damage. In recent years, there have been seen the introduction of infection sources via long- or short-term travelers having visited such countries; parasitic infection due to the consumption of food imports or raw meat and fish meat, which have become more available thanks to the advance in freezing and logistics technologies; and the transmission of parasitosis from pets. Under such circumstances, the incidence of parasitosis is on an upward trend again. Another problem is that immunodeficiency caused by mass administration of immunosuppressants, anticancer drugs, etc. or by AIDS etc. allows usually non-pathogenic or low-pathogenic parasites to express their pathogenicity and to cause opportunistic infection in hosts. Further, parasitosis in domestic animals, such as pigs, horses, cattle, sheep, dogs, cats and domestic fowls, is a universal and serious economic problem. That is, parasitic, infection of domestic animals causes anemia, malnutrition, debility, weight loss, and serious damage of intestinal tract walls, tissues and organs, and may result in decline in feed efficiency and productivity, leading to a great economic loss. Therefore, novel parasiticides, antiprotozoals or other endoparasite control agents have always been desired.